$headerHeight = .9rem
$bgGradient()
  background-image linear-gradient(90deg,#0af,#0085ff)
$ellipsis()
  overflow hidden
  white-space: nowrap
  text-overflow ellipsis

// 绝对定位使元素具有父级的宽高
$posFull()
  position absolute
  top 0
  left 0
  right 0
  bottom 0

// flex交叉轴居中
$flexVCenter()
  display flex
  align-items center

// flex全部居中
$flexCenter()
  display flex
  justify-content center
  align-items center

// flex主轴space-around 交叉轴居中
$flexHAround()
  display flex
  justify-content space-around
  align-items center